Molecular Genetics - Inheritance - Population Genetics - Medical Physiology - Social Issues

Introduction

Tourette syndrome (or Tourette Disorder) is a neurological disorder, which can be classified by tics (involuntary sudden movements and vocalizations), attention problems (which can be similar to those ADHD) and obsessive compulsiveness (which can be similar to OCD). There are over 200,000 people in the world currently with Tourette’s.  Only on the past few years has Tourette Syndrome (TS) been thought to be genetic. While the exact location of the TS gene has not been found yet, nor do scientists know yet which chromosome it is on, tests are currently being done to find the genome that causes TS. Among children, the symptoms for TS include tics, attention problems and obsessive compulsions. As the individual grows older, generally, tics start to decrease in severity and occurrence, however, other problems will arise like depression.

A French physician named Gilles de la Tourette discovered Tourrete Syndrome in 1885; Tourrete’s syndrome is a lifelong disorder that begins at around the age of five to seven, where such symptoms as ticks will appear. (Peschel and Howe, 1992.) The first patient is thought to be Marquise de Dampierre (1825), who was the oldest person to show symptoms for Tourrete’s. Now, one and six per thousand are thought to have TS.

Tourette Syndrome is difficult to quantify, because their symptoms (tics, attention, hyperactivity et al) vary from patient to patient, and can be severe or mild to the point where it is unnoticeable. It is so similar to other disorders such as ADHD (Attention Deficity Hyperactivity Disorder) and OCD (Obsessive Compulsions Disorder). While TS does affect a child’s attention, it does not affect the IQ of the TS patient. The TS patient can actually have an above average IQ and creativity level, although symptoms from TS prove to be an obstacle for children.

The genetics of Tourette syndrome is very complicated. Currently, an autosomal dominant gene is thought to be TS vulnerable, and other genes, the environment and the condition cause the variance in  phenotypic expressions. There are also various theories of “semi-dominance” and “semi-recesiveness” of the TS vulnerable gene, which will be furthur discussed in the inheritance section. The key may be finding a genetic marker (a biochemical abnormality that all TS patients share) to understanding the genetic risk factors of TS. The variance TS severity and occurrence indicates that there is far more to TS then the one genotype; along with the affect of other genes, the environment and the conditions in which the TS patient lives in is believed to affect the expression of the TS phenotype. For example, stress is thought to be the main contributor to the severity of TS. A TS patient under stress is more likely to display symptoms such as grunting, touching or jerking.

The key to finding the cause and genetics for TS will be to find the genome codes for the protein causes TS.  The most current research being done is genetics and neuroimagine of the brain and nervous system, and the psychopharmacology of TS. Research can lead to a clearer understanding of TS and how to improve treatments with fewer side-affects then the current therapies.

There are two possible sources of TS: the frontal cortex and the basal ganglia.  Alterations in the basal ganglia, abnormal pathways and neurochemicals are problems that which are thought to cause TS. Abnormalities in the frontal cortex would also result in tics. There are three neurotransmitters which have abnormal metabolism levels, which are thought to cause TS: norepinephrine, dopamine and serotonin.

Right now, there is no cure to TS. There are neuroleptic drugs and pharmacological therapy available to treat TS, however. The most common are Haloperidol, pimozide and clonidine.

There are many social issues involved in treating a patient with TS. The most important stage of a TS patient is between the ages of 6-18 when the patients brain and personality of changing. It is important to elevate the patient of as much stress as possible, as it is likely the biggest environmental cause to the phenotypical expression of TS. It is also important to give a lot of care, attention and love to the child, and build up their confidence as much as possible, as it is very hard to deal with many symptoms of Tourette’s.

French physician       Gilles de la Tourette,    the founder of   Tourette's Syndrome

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References

Related Disorders

OCB – Obsessive Compulsive Behaviour

This disorder s characterized by involuntary repetitive, intrusive, unwanted thoughts and ritual-like activities that cause distress or interfere with daily life. 37% of TS patients have OCB.

ADHD – Attention Deficit Hyperactive Disorder

At a young age, a patient with ADHD will be hyperactive, while at an older age, hyperactivity is replaced by tics. Currently, there is no evidence to suggest the relationship between ADHD and TS.

- http://www.tsa-usa.org/

Edward Lau, 2003.